Drying Napa Wells Limit Planting

Napa Valley has porous, volcanic soils and relies on groundwater for much of its irrigation supply.

A loss of groundwater has placed a portion of southeastern Napa County, Calif. out-of-bounds for new vineyards and is hampering residential development there, the Napa Valley Register reports.

The area has seen groundwater plummet 50 to 125 feet since 1975, according to a U.S. Geological Survey study released last year. The likely cause is years of use by the region's vineyards.

Water restrictions govern development in the area. Residential wells must be metered and are limited to roughly half an acre-foot per home per year. (An acre-foot is the amount of water used by about three homes per year, according to the Marin Municipal Water District.) Most permits for new vineyard plantings in the area are being denied.

One solution calls for a pipeline to carry recycled water to the area to recharge the water table. But it could take decades for the water to percolate down to the natural groundwater zone, experts say.

The water shortage has put winery expansion on hold, slowed residential development and has even led to the devaluation of land.

One vineyard experienced a $200,000 drop in appraised value after the USGS report came out, said Jim Lincoln of the Napa County Farm Bureau.